Aluminum cans are commonly used as containers for a wide variety of products, notably food and beverages. After manufacture, aluminum cans are washed, typically with an acidic cleaner, to remove aluminum fines and other residues. The cans are then rinsed with tap water, followed by deionized water, and dried in a hot air oven.
The rinsing of the aluminum cans in the cleaning treatment cycle results in the retention of a large amount of water on the surfaces of the cans. The retained water necessitates long oven drying time and high temperature to obtain efficient drying of the cans. Not only does this result in increased production time and cost, but water droplet formation increases the likelihood of water spot formation. Water spots decrease adhesion to subsequently applied overcoatings and finishes, such as decorative inks and overvarnishes.
Therefore, a chemical composition and method are highly desirable which provide water-break-free surface properties to aluminum and aluminum alloy surfaces and minimize the amount of water on such surfaces after being cleaned and rinsed, without adversely affecting adhesion properties. It would be ideal if the use of such a chemical composition could be incorporated into the treatment cycle, without necessitating changes to existing can manufacturing facilities.
The treatment should preferably provide the surface of an aluminum container, in particular aluminum beverage containers, with a clear, colorless, thin coating that retains the brightness of the aluminum surface, yet will not affect the taste of the food or beverage to be contained therein. More preferably, the treatment should reduce the surface tension, and thereby the amount, of water remaining on aluminum surfaces after washing and rinsing. Additionally, the treatment should provide the surface of the aluminum container with water-break-free surface characteristics so that water droplets do not form, thereby avoiding water spots. In the prevention of water spots, the treatment should not adversely affect, and preferably should optimize, adhesion to subsequently applied overcoatings and finishes. Moreover, the treatment should preferably decrease the time and temperature required to dry the aluminum surfaces, thereby reducing production time and cost.
These benefits are realized through use of the present inventive composition and method, which provide aluminum and aluminum alloy surfaces with water-break-free surface characteristics and reduce the quantity of water remaining on such surfaces after cleaning and rinsing. Water-break-free surface characteristics aid in the prevention of the formation of water droplets and, subsequently, water spots. Consequently, adhesion to subsequently applied overcoatings and finishes is optimized. Furthermore, the time and temperature required to dry the aluminum surfaces are decreased, thereby reducing production time and cost.